Split Stream Research Articles

Time-of-flight ICP-MS laser ablation zircon geochronology: assessment and comparison against quadrupole ICP-MS

This study presents U–Pb isotopic and trace element results from the mineral zircon measured by nanosecond laser ablation coupled to either a time-of-flight ICP-MS, a quadrupole ICP-MS or both via a split stream arrangement.

Disturbances in the Sm–Nd isotope system of the Acasta Gneiss Complex—Implications for the Nd isotope record of the early Earth

The whole rock 143Nd isotope record of the Acasta Gneiss Complex (AGC) has been used to argue for the development of both depleted mantle and enriched crustal reservoirs during the Hadean. The 147Sm–143Nd isotope compositions of rocks from AGC, however, fall on an array with an errorchron date of ∼3.3 Ga, despite the majority of samples yielding substantially older zircon U–Pb ages. This has led to the suggestion of a major Sm–Nd “resetting” event at this time in the AGC. To better understand the Sm–Nd bulk-rock systematics of the AGC, we investigate the U–Pb age and Sm–Nd isotope compositions of apatite and titanite from the AGC, using the laser ablation split stream (LASS) method. Apatite from all samples yield broadly similar U–Pb dates of ∼1.89 to 1.83 Ga, in agreement with resetting during the 1.9 Ga Wopmay orogen. The Sm–Nd isotope compositions of the apatite, however, lie off the WR errorchron and show a high degree of initial Nd isotope heterogeneity. Conversely, titanite Sm–Nd systematics are consistent with the ∼3.3 Ga whole rock errorchron further supporting Sm–Nd modification at ∼3.3 Ga. Taken together, these show that the oldest rocks in the AGC underwent at least two post-crystallization events (at 3.3 and 1.9 Ga) that modified the Sm–Nd isotope system. These results also demonstrate the relative mobility of the Sm–Nd isotope system during orogenic events, which may compromise the ability to determine robust bulk-rock 143Nd isotope signatures.

Cell-Based Metabolomics for Untargeted Screening and Prioritization of Vertebrate-Active Stressors in Streams Across the United States.

The U.S. Geological Survey and the U.S. Environmental Protection Agency have assessed contaminants in 38 streams across the U.S., using an extensive suite of target-chemical analysis methods along with a variety of biological effects tools. Here, we report zebrafish liver (ZFL) cell-culture based NMR metabolomic analysis of these split stream samples. We used this untargeted approach to evaluate the sites according to overall impact on the ZFL metabolome and found that neither the total number of organics detected at the sites, nor their cumulative concentrations, were good predictors of these impacts. Further, we used partial least squares regression to compare ZFL endogenous metabolite profiles to values for 455 potential stressors (organics, inorganics, and physical properties) measured in these waters and found that the profiles covaried with at most 280 of the stressors, which were subsequently ranked into quartiles based on the strength of their covariance. While contaminants of emerging concern (CECs) were well represented in the top, most strongly covarying quartile-suggesting considerable potential for eliciting biological responses at these sites-there was even higher representation of various well-characterized legacy contaminants (e.g., PCBs). These results emphasize the importance of complementing chemical analysis with untargeted bioassays to help focus regulatory efforts on the most significant ecosystem threats.

A combined chemical imaging approach using (MC) LA-ICP-MS and NIR-HSI to evaluate the diagenetic status of bone material for Sr isotope analysis.

This paper presents a combination of elemental and isotopic spatial distribution imaging with near-infrared hyperspectral imaging (NIR-HSI) to evaluate the diagenetic status of skeletal remains. The aim is to assess how areas with biogenic n(87Sr)/n(86Sr) isotope-amount ratios may be identified in bone material, an important recorder complementary to teeth. Elemental (C, P, Ca, Sr) and isotopic (n(87Sr)/n(86Sr)) imaging were accomplished via laser ablation (LA) coupled in a split stream to a quadrupole inductively coupled plasma mass spectrometer (ICP-QMS) and a multicollector inductively coupled plasma mass spectrometer (MC ICP-MS) (abbreviation for the combined method LASS ICP-QMS/MC ICP-MS). Biogenic areas on the bone cross section, which remained unaltered by diagenetic processes, were localized using chemical indicators (I(C)/I(Ca) and I(C) × 10/I(P) intensity ratios) and NIR-HSI at a wavelength of 1410nm to identify preserved collagen. The n(87Sr)/n(86Sr) isotope signature analyzed in these areas was in agreement with the biogenic bulk signal revealed by solubility profiling used as an independent method for validation. Elevated C intensities in the outer rim of the bone, caused by either precipitated secondary minerals or adsorbed humic materials, could be identified as indication for diagenetic alteration. These areas also show a different n(87Sr)/n(86Sr) isotopic composition. Therefore, the combination of NIR-HSI and LASS ICP-QMS/MC ICP-MS allows for the determination of preserved biogenic n(87Sr)/n(86Sr) isotope-amount ratios, if the original biogenic material has not been entirely replaced by diagenetic material. Graphical abstract ᅟ.

Partial Carbon Capture by Absorption Cycle for Reduced Specific Capture Cost

For a sustainable-energy system, the industrial carbon emission should be zero or close to it. The partial capture of CO2, i.e., capturing only a share of the CO2, is discussed as an option for initiating the transition toward the decarbonization of industry by reducing the CO2 mitigation cost at industrial sites. This work models two approaches to achieving partial capture based on amine absorption: (1) capturing 90% CO2 from a split stream of the flue gas or (2) capturing less CO2 (≪90%) from the total flue-gas flow. A techno-economic analysis is carried out that considers scale, CO2 concentration, and process configurations (absorber intercooling and rich solvent splitting) when comparing the cost of partial capture to full capture, i.e., capturing close to all CO2 from the entire gas. Besides lowering absolute costs, the study shows that partial capture from CO2-rich gases may also lower specific cost (€ per tonne of CO2 captured) compared to full capture, despite the economy of scale, during certain market conditions. Operating expenditures, especially the cost of steam, are found to be dominating cost factors for partial capture, even for capture down to 200 000 tonnes per year.

Lower urinary tract symptoms and prostate cancer: is PSA testing in men with symptoms wise?

The best evidence to date shows that, overall, the harms of prostate cancer screening in asymptomatic men outweigh the benefits. A 2013 Cochrane review found that screening asymptomatic men did not save lives from the disease, and leads to detection of indolent prostate cancers that would not have gone on to cause harm in a man’s lifetime.1 This is known as overdiagnosis. Further weight was added to the results of the Cochrane review in the recent 10-year follow-up results from the cluster randomised trial of PSA testing for prostate cancer (CAP), which found that one-off PSA testing of asymptomatic men did not save lives from prostate cancer.2 For symptomatic men, however, the clinical situation is different. Current clinical guidelines from the National Institute for Health and Care Excellence (NICE) recommend that GPs consider a PSA test and digital rectal examination (DRE) in men presenting with lower urinary tract symptoms (LUTS) to investigate suspected prostate cancer.3 For the purposes of this article we defined LUTS as: nocturia, urgency, frequency, incomplete voiding, intermittency, terminal dribble, hesitancy, straining, weak or split stream, and/or post-micturation dribble. LUTS are very common in men, and have been estimated to be present in around 80% of men aged >60 years.4 The 2013 Cochrane review stated that ‘... the presence of LUTS, typically due to benign prostatic obstruction, are very common in the ageing male and are not considered to increase prostate …

Zircon as a metamorphic timekeeper: A case study from the Caledonides of central Norway

During metamorphism, inherited or detrital zircon grains commonly serve as a template onto which new generations of metamorphic zircon precipitates, charting successive episodes in the thermal history of rocks. In addition, chemical modification of pre-metamorphic zircon can leave an imprint in the U–Pb systematics. We present a case study from a sample of migmatitic amphibole–biotite gneiss from central Norway that contains zircon grains that chart much of the history of an entire orogenic episode, not only through generation of new zircon, but also resetting of the U–Pb system via radiogenic-Pb loss. The investigated gneiss, from the Helgeland Nappe Complex, within the Uppermost Allochthon of the Scandinavian Caledonides records a prolonged metamorphic evolution. Phase equilibria modelling implies peak metamorphic conditions of 7.5–8.0 kbar and 650–675 °C, consistent with low-degree partial melting and the presence of small volumes of leucosome. Laser ablation split stream analysis that simultaneously measures U–Pb, REE and Lu–Hf in the same volume of zircon, yields a range of analyses that spread along concordia. A zircon population between 485 and 443 Ma is characterized by faded and blurred oscillatory-zoned domains that have gained nonformula elements. These analyses are interpreted to indicate the presence of reactive solutions during this time period that led to leaching and mobility of Pb. Another texturally distinct zircon component yields an age of 478 ± 4 Ma, has typical igneous REE zircon profiles, and records low apparent alpha doses, interpreted to reflect new zircon growth during migmitization. A further population of zircon rims and discrete grains yields an age of 453 ± 2 Ma, interpreted as a later episode of zircon growth during high-grade metamorphism. A final set of zircon overgrowths yield an age of 439 ± 3 Ma, also interpreted to reflect new metamorphic growth. Many zircon growth phases in this rock have similar REE patterns, implying broadly isochemical metamorphism, consistent with the evidence for only limited partial melting. Furthermore, the Hf isotopic signature in the analyzed zircon grains suggests that there was no release of radiogenic Hf during metamorphism. The metamorphic zircon in the studied rock records several episodes of growth and/or alteration over a period of >40 Ma that was related to protracted destruction of the Iapetus Ocean. In the context of regional data, the new results suggest that the Helgeland Nappe Complex, which is generally considered to be exotic to Baltica, underwent geographically widespread, long-lived Ordovician high-temperature metamorphism. This record of metamorphism is distinct from that recorded by tectonostratigraphically lower units, which are conventionally regarded to have been derived from Baltica. The results shed light on the assembly of the Scandinavian Caledonides and show that zircon from individual samples may be used to unravel complex orogenic histories.

Trace Element and U–Pb Core Age for Zircons from Western Meiganga Gold Placer, Cameroon: Their Genesis and Archean-Proterozoic Sources

Trace element concentrations and U–Pb ages were obtained using Laser Ablation Split Stream Method from the core of 115 zircon grains from the western Meiganga gold placer deposit. The data was used to characterize zircon, to understand the history of crystallization and to locate source rocks within the local and regional geological settings. Zircon trace element geochemistry was used to distinguish between magmatic and metamorphic affinity. The magmatic zircons have characteristics compatible with their probable origin from granitoid, syenite, tonalite, charnockite and mafic to ultramafic rocks. The metamorphic zircons composition is compatible with growth from anatectic melts and by sub-solidus crystallization in equilibrium with garnet. The zircon ages reveal Archean, Paleoproterozoic, Mesoproterozic, and Neoproterozoic events with the principal source could mainly belong to Paleoproterozoic magmatic lineage. Some of the Paleoproterozoic magmatic zircons were probably sourced from two mica granite found within the local geology, whereas the remaining zircons have features indicating source rocks within the Congo Craton. We suggest that the geologic history of these zircons is related to crustal-scale magmatic and/or tectono-metamorphic events, possibly linked to Eburnean and Pan-African orogeny.

Using the magmatic record to constrain the growth of continental crust—The Eoarchean zircon Hf record of Greenland

Southern West Greenland contains some of the best-studied and best-preserved magmatic Eoarchean rocks on Earth, and these provide an excellent vantage point from which to view long-standing questions regarding the growth of the earliest continental crust. In order to address the questions surrounding early crustal growth and complementary mantle depletion, we present Laser Ablation Split Stream (LASS) analyses of the U–Pb and Hf isotope compositions of zircon from eleven samples of the least-altered meta-igneous rocks from the Itsaq (Amîtsoq) Gneisses of the Isukasia and Nuuk regions of southern West Greenland. This analytical technique allows a less ambiguous approach to determining the age and Hf isotope composition of complicated zircon. Results corroborate previous findings that Eoarchean zircon from the Itsaq Gneiss (∼3.85 Ga to ∼3.63 Ga) were derived from a broadly chondritic source. In contrast to the Sm–Nd whole rock isotope record for southern West Greenland, the zircon Lu–Hf isotope record provides no evidence for early mantle depletion, nor does it suggest the presence of crust older than ∼3.85 Ga in Greenland.Utilizing LASS U–Pb and Hf data from the Greenland zircons studied here, we demonstrate the importance of focusing on the magmatic (rather than detrital) zircon record to more confidently understand early crustal growth and mantle depletion. We compare the Greenland Hf isotope data with other Eoarchean magmatic complexes such as the Acasta Gneiss Complex, Nuvvuagittuq greenstone belt, and the gneissic complexes of southern Africa, and all lack zircons with suprachondritic Hf isotope compositions. In total, these data suggest only a very modest volume of crust was produced during (or survived from) the Hadean and earliest Eoarchean. There remains no record of planet-scale early Earth mantle depletion in the Hf isotope record prior to 3.8 Ga.

Foundering Triggered by the Collision of India and Asia Captured in Xenoliths

AbstractXenoliths that erupted in the SE Pamir of Tajikistan from 1000 to 1050°C and 90 km depth illuminate what happens when crust founders into the mantle. 40Ar/39Ar dating of minerals from the xenoliths and volcanic host rocks of the shoshonitic Dunkeldik pipe and dike field indicates eruption at 11.2 ± 0.2 Ma. U‐Pb and trace element laser‐ablation split stream inductively coupled plasma mass spectrometry of zircon shows that the igneous and metasedimentary xenoliths were likely derived from the crustal section into which they were intruded: the Jurassic‐Cretaceous Andean‐style magmatic arc and its Proterozoic‐Mesozoic host rocks along the southern margin of Asia. Recrystallization of these zircons was extensive, yielding a range of dates down to 11 Ma. The zircons show distinct changes in Eu anomaly, Lu/Gd ratio, and Ti concentrations compatible with garnet growth and minimal heating at 22–20 Ma and then 200‐300°C of heating, ~25 km of burial, and alkali‐carbonate melt injection at 14–11 Ma. These changes are interpreted to coincide with (i) heat input due to Indian slab breakoff at ~22–20 Ma and (ii) rapid thickening and foundering of the Pamir lithosphere at 14‐11 Ma, prior to and synchronous with collision between deep Indian and Asian lithospheres beneath the Pamir.

Development of energy-efficient processes for natural gas liquids recovery

A new NGL (natural gas liquids) recovery process configuration is proposed which can offer improved energy efficiency and hydrocarbon recovery. The new process configuration is an evolution of the conventional turboexpander processes with the introduction of a split stream transferring part of the feed to the demethanizer column. In this way additional heat recovery is possible which improves the energy efficiency of the process. To evaluate the new process configuration a number of different NGL recovery process configurations are optimized and compared using a process simulator linked interactively with external optimization methods. Process integration methodology is applied as part of the optimization to improve energy recovery during the optimization. Analysis of the new process configuration compared with conventional turbo-expander process designs demonstrates the benefits of the new process configuration.

Combining Nd isotopes in monazite and Hf isotopes in zircon to understand complex open-system processes in granitic magmas

Abstract Mapping the age and trace element and Sm-Nd isotope compositions of monazite grains from a peraluminous Cretaceous granite using laser ablation–split stream analysis reveals a wide range in Nd isotope and rare earth element (REE) compositions within and between single grains. These data corroborate isotopic variability indicated by Hf isotope analysis of zircon in the same granite sample. The REE variations indicate that monazite grew during fractional crystallization. Hf and Nd isotopes indicate that the granitic magma was generated from at least two distinct Proterozoic sources of approximately the same age: one component that had highly radiogenic initial 176Hf/177Hf and 143Nd/144Nd and a second component that was notably less radiogenic. This study highlights the utility of in situ REE and Sm-Nd isotope data in monazite in magmatic systems. Further, it refines the zircon-based constraints on magmatic processes because of sensitivity of light REEs to fractional crystallization, lower probability of complications owing to inheritance, and smaller analytical volumes required.

Development of routines for simultaneous in situ chemical composition and stable Si isotope ratio analysis by femtosecond laser ablation inductively coupled plasma mass spectrometry

Stable metal (e.g. Li, Mg, Ca, Fe, Cu, Zn, and Mo) and metalloid (B, Si, Ge) isotope ratio systems have emerged as geochemical tracers to fingerprint distinct physicochemical reactions. These systems are relevant to many Earth Science questions. The benefit of in situ microscale analysis using laser ablation (LA) over bulk sample analysis is to use the spatial context of different phases in the solid sample to disclose the processes that govern their chemical and isotopic compositions. However, there is a lack of in situ analytical routines to obtain a samples' stable isotope ratio together with its chemical composition. Here, we evaluate two novel analytical routines for the simultaneous determination of the chemical and Si stable isotope composition (δ30Si) on the micrometre scale in geological samples. In both routines, multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) is combined with femtosecond-LA, where stable isotope ratios are corrected for mass bias using standard-sample-bracketing with matrix-independent calibration. The first method is based on laser ablation split stream (LASS), where the laser aerosol is split and introduced simultaneously into both the MC-ICP-MS and a quadrupole ICP-MS. The second method is based on optical emission spectroscopy using direct observation of the MC-ICP-MS plasma (LA-MC-ICP-MS|OES). Both methods are evaluated using international geological reference materials. Accurate and precise Si isotope ratios were obtained with an uncertainty typically better than 0.23‰, 2SD, δ30Si. With both methods major element concentrations (e.g., Na, Al, Si, Mg, Ca) can be simultaneously determined. However, LASS-ICP-MS is superior over LA-MC-ICP-MS|OES, which is limited by its lower sensitivity. Moreover, LASS-ICP-MS offers trace element analysis down to the μg g−1-range for more than 28 elements due to lower limits of detection, and with typical uncertainties better than 15%. For in situ simultaneous stable isotope measurement and chemical composition analysis LASS-ICP-MS in combination with MC-ICP-MS is the method of choice.

Tracking coarse-grained gravity flows by LASS-ICP-MS depth-profiling of detrital zircon (Aveto Formation, Adriatic foredeep, Italy)

Coarse-grained gravity flow deposits are quite common in the stratigraphic record, but their capability in transporting cobbles and boulders at great distance from the eroding sources is still poorly assessed. Here, we tackle this issue by the analysis of coarse-grained gravity flow deposits of the Aveto Formation, deposited in the Early Oligocene Adriatic foredeep and now exposed in the accretionary wedge of the Northern Apennines (Italy). We combine field observations and provenance constraints provided by Laser Ablation Split Stream (LASS)-ICP-MS depth-profiling of detrital zircon grains. We found that the polymodal grain-age distributions in the analyzed samples, dominated by Periadriatic, Variscan and Caledonian age populations, also include Late Cretaceous to Paleocene ages associated to thin epitaxial overgrowths on older zircon cores. These overgrowths display Th/U and REE patterns consistent with a metamorphic origin, and provide a diagnostic fingerprint that indicates the Bergell area in the Central Alps as the only viable source of coarse detritus, including cobbles and boulders of magmatic and metamorphic rocks, transported by gravity flows towards the nascent Adriatic foredeep. Our results provide not only pin-points for a reliable paleotectonic reconstruction of the Bergell-Aveto source-to-sink system, one of the most remarkable features of the Oligocene Adria-Europe plate boundary, but also compelling evidence for ∼300 km axial transport by gravity flows experienced by coarse detritus derived from the Oligocene Central Alps. The eruptions of the Bergell volcanic complex provided abundant pyroclastic material variably mixed with metamorphic detritus, that was quickly funneled into submarine canyons triggering southward-directed gravity flows. Active tectonics, pyroclastic material provided by volcanic eruptions, steep canyons close to the shoreline and the presence of fault-controlled submarine troughs, may effectively promote the long-distance transport of coarse material by gravity flows not only in the Oligocene, but also today.

Urine Pain

HISTORY: 19-year-old male collegiate lacrosse player presented to the training room with abdominal pain, emesis, and gross hematuria following a cross-check to his abdomen during a game one day prior. Symptoms cleared with a negative urine dipstick 48 hours after injury and he was cleared for competition. One week later, he was cross-checked again in the abdomen, resulting in similar symptoms including hematuria, abdominal pain, anorexia, and emesis. He denied significant medical history, denied taking medications, previous trauma, surgeries or smoking. He reported a history of split urinary stream. Symptoms persisted 4 days post injury at which time he was sent to the ER for further evaluation. PHYSICAL EXAM: Gen: No acute distress, well-appearing GU: uncircumcised penis, normal descended testes bilaterally, no mass/hernias, normal phallus, normal epididymis, normal scrotum, urethral meatus normal without blood. Abdomen: no ecchymosis, normal bowel sounds, abdomen tender to palpation in the LUQ, suprapubic area, and left flank. No rigidity, guarding, or organomegaly. DIFFERENTIAL DIAGNOSIS: Bladder wall hematoma/contusion/perforation Renal contusion Splenic injury Ureteral/urethral Injury FINAL/WORKING DIAGNOSIS: Abdominal pain, hematuria, and trace intraperitoneal free fluid status post blunt abdominal trauma without evidence of bladder, ureteral, urethral, or kidney injury TESTS AND RESULTS: CBC and BMP normal Urine analysis moderate blood with >50 RBCs FAST ultrasound - normal CT abdomen/pelvis with contrast - trace intraperitoneal free fluid behind bladder, no bladder injury CT/cystogram- negative for bladder rupture or injury TREATMENT AND OUTCOMES: Urology consulted in the ED and discharged following CT cystogram failed to show organ damage. At one week, he was asymptomatic and had a negative urine dipstick. Urology suggested cystoscopy if hematuria re-occurred. He was cleared for gradual return to play and recommended to use abdominal guarding in the future. While hematuria following abdominal trauma is not rare, subsequent free fluid spurs questions of whether there were predisposing factors (i.e. stricture) or if an acute injury resulted in the clinical and diagnostic findings. This is an unusual problem following such an injury and a unique workup with questions on his safe return to play.

Thermochronology of extensional orogenic collapse in the deep crust of Zealandia

The exhumed Fiordland sector of Zealandia offers a deep-crustal view into the life cycle of a Cordilleran-type orogen from final magmatic construction to extensional orogenic collapse. We integrate U-Pb thermochronologic data from metamorphic zircon and titanite with structural observations from >2000 km 2 of central Fiordland to document the tempo and thermal evolution of the lower crust during the tectonic transition from arc construction and crustal thickening to crustal thinning and extensional collapse. Data reveal that garnet granulite facies metamorphism and partial melting in the lower crust partially overlapped with crustal thickening and batholith construction during emplacement of the Western Fiordland Orthogneiss (WFO) from 118 to 115 Ma. Metamorphic zircons in metasedimentary rocks yield 206 Pb/ 238 U (sensitive high-resolution ion microprobe–reverse geometry) dates of 116.3–112.0 Ma. Titanite laser ablation split stream inductively coupled plasma–mass spectrometry chronology from the same rocks yielded complex results, with relict Paleozoic 206 Pb/ 238 U dates preserved at the margins of the WFO. Within extensional shear zones that developed in the thermal aureole of the WFO, titanite dates range from 116.2 to 107.6 Ma and have zirconium-in-titanite temperatures of ∼900–750 °C. A minor population of metamorphic zircon rims and titanites in the Doubtful Sound region yield younger dates of 105.6–102.3 Ma with corresponding temperatures of 740–730 °C. Many samples record Cretaceous overdispersed dates with 5–10 m.y. ranges. Core-rim traverses and grain maps show complex chemical and temporal variations that cannot easily be attributed to thermally activated volume diffusion or simple core-rim crystallization. We interpret these Cretaceous titanites not as cooling ages, but rather as recording protracted growth and/or crystallization or recrystallization in response to fluid flow, deformation, and/or metamorphic reactions during the transition from garnet granulite to upper amphibolite facies metamorphism. We propose a thermotectonic model that integrates our results with structural observations. Our data reveal a clear tectonic break at 108–106 Ma that marks a change in processes deep within the arc. Prior to this break, arc construction processes dominated and involved (1) emplacement of mafic to intermediate magmas of the Malaspina and Misty plutons from 118 to 115 Ma, (2) contractional deformation at the roof of the Misty pluton in the Caswell Sound fold-thrust belt from 117 to 113 Ma, and (3) eclogite to garnet granulite facies metamorphism and partial melting over >8 m.y. from 116 to 108 Ma. These processes were accompanied by complex patterns of lower crustal flow involving both horizontal and vertical displacements. After this interval, extensional orogenic collapse initiated along upper amphibolite facies shear zones in the Doubtful Sound shear zone at 108–106 Ma. Zircon and titanite growth and/or crystallization or recrystallization at this time clearly link upper amphibolite facies metamorphism to mylonitic fabrics in shear zones. Our observations are significant in that they reveal the persistence of a hot and weak lower crust for ≥15 m.y. following arc magmatism in central Fiordland. We propose that the existence of a thermally weakened lower crust within the Median Batholith was a key factor in controlling the transition from crustal thickening to crustal thinning and extensional orogenic collapse of the Zealandia Cordillera.

GIS-Based Reach File Generation for Efficient TMDLs Implementation

The ability to generate stream network data is essential to conducting fast searches and accurate analyses to obtain various types of environmental information on individual streams required to implement a Total Maximum Daily Loads (TMDLs) program. This study presents a major concept, an algorithm, and a procedure to build such stream network data, the Korean Reach File (KRF), based on a geographic information system (GIS). For the generation of the KRF’s graphic data, a 1:25,000 scale nationwide river/stream map, a watershed map, and a polygon type administrative district map were utilized to delineate stream flow lines, split stream reaches, and assign unique identifiers. To generate the KRF’s attribute data, we designed attribute tables for all the graphic data. All the attributes were inputted to each item of graphic data according to designed attribute input rules and the KRF was generated in a shapefile format. To evaluate the accuracy of the graphic data, we compared the stream lengths of the KRF on national level streams with actually surveyed stream lengths. The study results showed the graphic and attribute data that were generated for the four major river basins with a total stream length of 21,163 km. The Mean Absolute Percentage Error (MAPE) was about 3.8%, and we confirmed that the KRF network data were generated with relatively high spatial accuracy. The KRF’s applicability for the TMDLs was also discussed with examples. In the future, a GIS-based management system using the KRF should be developed to support TMDLs more efficiently.

Simultaneous multi-element and isotope ratio imaging of fish otoliths by laser ablation split stream ICP-MS/MC ICP-MS

The simultaneous retrieval of spatially resolved information on the elemental content and isotope ratios from the same sampling spot (e.g. in incrementally grown biological material) still represents an analytical challenge.

Extracting thermal histories from the near-rim zoning in titanite using coupled U-Pb and trace-element depth profiles by single-shot laser-ablation split stream (SS-LASS) ICP-MS

A method for depth profiling using single-shot laser-ablation split stream (SS-LASS) ICP-MS is developed to simultaneously measure U-Pb age and trace-element concentrations in titanite. Simple semi-infinite, 1-D half-space diffusion models were applied to near-rim, trace-element zoned domains in titanite to distinguish between cooling and (re)crystallization ages and investigate the potential for preservation of thermally mediated diffusive loss profiles. These data illustrate the need to measure multiple trace elements with varying diffusivities to interpret a mineral's thermal history resulting from the non-unique nature of 1-D diffusion models where both temperature and time are unknown. A case study of titanites from two Pamir Plateau gneiss domes indicates they underwent ≥25 Myr of amphibolite and granulite facies metamorphism yet did not experience significant volume diffusion modification following (re)crystallization. The interpretation of prolonged (re)crystallization rather than diffusion allows for high-resolution, near-rim temperature-time histories to be extracted using U-Pb dates and Zr4+ apparent temperatures by SS-LASS.

Single-shot laser ablation split stream (SS-LASS) petrochronology deciphers multiple, short-duration metamorphic events

Single-shot laser ablation split stream (SS-LASS) petrochronology offers spatial resolution of <1μm per (surface) analysis. This enables the technique to interrogate metamorphic zircon overgrowths that are very thin, or that preserve a composite age structure. To demonstrate the advantages of SS-LASS, the technique was applied to metamorphic zircon overgrowths in five rocks from the Cordillera de la Costa, Venezuela. In these rocks, SS-LASS was able to decipher discrete, short-duration (<106yr) zircon growth events at c. 33.0, c. 28.3, c. 23.0 and c. 18.2Ma. Comparison with existing geo-/thermochronology suggests that the SS-LASS dates represent (hydro)thermal events that mark distinct episodes of tectonism affecting the northern margin of South America.With an external error of 5% incorporated into isotope ratios (as required to achieve satisfactory analytical precision), SS-LASS dates for reference materials were accurate to within 1.5% of published values. The SS-LASS technique is thus, in favorable cases, capable of providing <106yr resolution for Cenozoic rocks. Methods in ‘geospeedometry’—which employ forward models to reproduce observed diffusion length scales—have obtained anomalously short time scales of 104–106yr for metamorphism. The high spatial and temporal resolution of SS-LASS offers tremendous promise for investigating the veracity of these claims.